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US Army Corps of Engineers Hydrologic Engineering Center. Introduction to HEC-HMS. Bill Scharffenberg Hydrologic Engineering Center. Objectives. Become familiar with the program and learn basic concepts of program organization, data components, and simulation runs.

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introduction to hec hms

US Army Corps

of Engineers

Hydrologic Engineering Center

Introduction toHEC-HMS

Bill Scharffenberg

Hydrologic Engineering Center

  • Become familiar with the program and learn basic concepts of program organization, data components, and simulation runs.
  • Understand the different hydrologic elements and the methods available for each one.
  • See the different types of results visualization and statistical summaries.
  • Preview advanced capabilities.
program scope
Program Scope
  • Designed to simulate watershed hydrology.
    • Surface water modeling.
    • From meteorology to watershed outlet.
  • Tool kit of options.
    • Generalized modeling.
    • Mathematical model choices.
    • Analysis tools.
  • Graphical user interface
    • Map of the watershed.
    • Point-and-edit for entering and updating data.
    • Graph and table displays of simulation results.
program limitations
Program Limitations
  • Deterministic models.
  • Uncoupled models.
    • Evapotranspiration-infiltration.
    • Infiltration-baseflow.
  • No aquifer interactions.
  • Constant parameter values.
  • Dendritic stream systems.
    • Flow splits possible but limited capability.
  • No downstream flow influence or reversal.
    • Backwater possible but only if contained within a reach.
  • Container for main components.
    • Basin model.
    • Meteorologic model.
    • Control specifications.
  • Also holds additional components.
    • Time-series gages.
    • Paired data functions.
    • Grid data sets.
  • Provides analysis tools.
    • Parameter estimation using optimization theory.
    • Depth-area analysis for frequency storm.
  • Subdirectory name
data management
Data Management
  • Configuration data and parameters.
    • Files within the project directory.
    • Automatically created, saved, loaded, etc.
  • Data Storage System HEC-DSS.
    • Time-series and paired data can be manually entered or retrieved from external files.
    • Grid data can only be retrieved from external files.
    • All time-series results computed during a simulation.
  • Automatic data handling.
    • Units conversion.
    • Interpolation or accumulation.
main components
Main Components
  • Basin model gives the physical description of the watershed.
    • Subbasin: watershed catchments where rain falls.
    • Reach: rivers and streams.
    • Reservoir: dams and lakes.
    • Junction: confluence.
    • Diversion: bifurcations and withdrawls.
    • Source: springs and other model sinks.
    • Sink: outlets and terminal lakes.
  • Meteorologic model describes atmospheric conditions over the watershed land surface.
    • Precipitation.
    • Potential evapotranspiration.
    • Snowmelt.
  • Control specifications: Time control during a simulation run.
program application
Program Application
  • Create a new project.
  • Enter time-series, paired data, and grid data.
  • Create a basin model.
  • Create a meteorologic model.
  • Create control specifications.
  • Create and compute a simulation run.
  • View results.
  • Create other alternatives, compute, and compare results.
  • Save the project and exit.
subbasin infiltration
Subbasin Infiltration
  • Loss rate methods:
    • Deficit constant.
    • Exponential.
    • Green Ampt.
    • Gridded deficit constant.
    • Gridded SCS.
    • Gridded SMA.
    • Initial constant.
    • SCS curve number.
    • Smith Parlange.
    • Soil moisture accounting.
subbasin surface runoff
Subbasin Surface Runoff
  • Unit hydrograph methods:
    • Clark.
    • SCS.
    • S-graph.
    • Snyder.
    • User-specified.
  • Other methods:
    • Kinematic wave.
    • ModClark distributed.
subbasin baseflow
Subbasin Baseflow
  • Baseflow methods:
    • Bounded recession.
    • Linear reservoir.
    • Monthly constant.
    • Nonlinear Boussinesq.
    • Recession.
  • Routing methods:
    • Kinematic wave
    • Lag
    • Modified Puls
    • Muskingum
    • Muskingum-Cunge
    • Straddle stagger
  • Loss/gain methods:
    • Constant.
    • Percolation.
  • Routing methods:
    • Storage curve.
    • Outlet structures.
    • Specified release.
  • Possible structures:
    • Gated spillway (0 to 10).
    • Overflow (0 to 10).
    • Outlet (0 to 10).
    • Pump (0 to 10).
    • Dam break (0 or 1).
  • Historical methods:
    • Gage weights.
    • Inverse distance.
    • User-specified.
    • Gridded.
  • Hypothetical methods:
    • Frequency storm.
    • SCS storm.
    • Standard project storm.
  • Available methods:
    • Gridded Priestley-Taylor.
    • Monthly average.
    • Priestley-Taylor.
  • Temperature index method.
    • Subbasin band approach.
    • Gridded approach.
simulation run
Simulation Run
  • Consists of one basin model, meteorologic model, and control specifications.
    • Precipitation or outflow ratio option.
    • Start states option.
    • Save states option.
  • View results for the current simulation run using menu or toolbar
    • Global summary table.
  • View results for one element in the current simulation run using the menu, toolbar, or basin map.
    • Graph, summary table, time-series table.
  • View custom graphs and time-series tables for elements in different simulation runs using the Watershed Explorer.
continuous simulation
Continuous Simulation
  • "Event" simulation is only concerned with hydrology during and immediately after a storm.
  • "Continuous" simulation includes events and the time between them, up to several decades at a time.
  • Loss rate methods:
    • Deficit constant.
    • Soil moisture accounting.
  • May be needed to satisfy some study goals:
    • Reproduce frequency curve.
    • Water balance estimates.
    • Flow rates or volumes beyond instantaneous peaks.
gridded simulation
Gridded Simulation
  • Precipitation, evapotranspiration, and snowmelt are defined on a grid cell basis.
  • Infiltration and excess precipitation is computed separately for each cell.
  • ModClark transform method is used to process excess precipitation into runoff at the subbasin outlet.
  • Better definition of subbasin response:
    • Storm is small compared to the subbasin size.
    • Storm is very heterogeneous.
advanced reservoir features
Advanced Reservoir Features
  • Interior flood protection projects.
    • Represents a pond on the "dry" side of a levee or floodwall where local drainage water accumulates.
    • Include culverts to pass water through the levee into the river when the river stage is low.
    • Include pumps to move water over the levee during floods.
  • Dam break evaluations.
    • Simulate the dam release from piping or overtopping failures.
parameter estimation
Parameter Estimation
  • Automated tool for estimating parameters when observed flow is available.
  • "Objective function" measures how well the computed and observed flow hydrographs match.
  • "Search method" uses the objective function as input to an algorithm that determines how to adjust parameter values to find the optimum match.
  • Can provide good estimates for some parameters:
    • Infiltration initial conditions and parameters.
    • Unit hydrograph parameters.
    • Baseflow initial conditions and parameters.
    • Some routing parameters.
depth area analysis
Depth-Area Analysis
  • Frequency storm is often used for estimating flows due to the 100-yr storm or other return intervals.
  • Large watersheds often have many locations where flow estimates are required.
  • It can be tedious to develop storms with the correct area for each of the locations.
  • Analysis tool uses a simulation run and automatically adjusts the storm area for each selected location.
gis preprocessor
GIS Preprocessor
  • HEC-GeoHMS can be used to create basin models using terrain data.
  • Start with a digital elevation model.
  • Select a watershed outlet and then GeoHMS automatically delineates the watershed border and preliminary subbasins outlines.
  • Adjust subbasin outlets.
  • GeoHMS creates a basin model that can be imported into HEC-HMS and also creates database table of parameters that can be estimated from terrain and other supplemental data layers.